Image display

ABSTRACT

This invention is an image display device for performing color display of an image using two spatial light modulators. The image display device has a first spatial light modulator ( 52 ) for modulating a first wavelength range component of illuminating light from an illuminating light source ( 10 ), dichroic mirrors ( 40 ), ( 41 ) for separating second and third wavelength range components of the illuminating light and condensing the respective wavelength range components, a second spatial light modulator ( 50 ) for modulating the second and third wavelength range components, and a dichroic mirror ( 60 ) for combining modulated light emitted from the first and second spatial light modulators ( 52 ), ( 50 ).

TECHNICAL FIELD

[0001] This invention relates to an image display device, andparticularly to a projection-type image display device and a virtualimage display device.

BACKGROUND ART

[0002] Conventionally, with respect to an image display device such as aprojection-type image display device or a virtual image display deviceusing a spatial light modulator, the following proposals have been inorder to realize color image display.

[0003] (1) One spatial light modulator is used and pixels for R (red), G(green) and B (blue), respectively, are spatially arranged in thespatial light modulator. Color image display is realized by using atleast these three basic color pixels as a set and making each colorpixel smaller than a size that can be recognized with the spatialresolution of human eyes.

[0004] Systems for this include a system in which a color filter isprovided for each pixel, a color filterless system using a dichroicmirror and a microlens array, for example, as described in JP-A-4-60538,and a color filterless system using a holographic optical element, forexample, as described in JP-A-9-189809.

[0005] (2) In a “field sequential color system” where one spatial lightmodulator is used and three colors R (red), G (green) and B (blue) ofilluminating light illuminating the element is time-divisionallyswitched, color image display is realized by at least shortening theswitching time to less than a time that can be recognized with thetemporal resolution of human eyes. A fundamental difference between thissystem and the first system is that the spatial light modulatorconstantly modulates only one of R (red), G (green) and B (blue) atarbitrary timing over the entire display area. As the element fortime-divisionally switching the color components, for example, “TimeSequential System” manufactured by Color Link may be used.

[0006] (3) Color image display is realized by using three spatial lightmodulators for R (red), G (green) and B (blue), respectively, andcausing color combination means to combine images of the respectivecolors emitted from these spatial light modulators, for example, asdescribed in JP-A-6-202004.

[0007] (4) Color image display is realized by combining the secondsystem with the third system, that is, by using a first spatial lightmodulator that constantly modulates only one of R (red), G (green) and B(blue) at arbitrary timing and a second spatial light modulator thatmodulates the remaining two colors in the “field sequential colorsystem”. Modulated light from the first spatial light modulator andmodulated light from the second spatial light modulator are combined bycolor combination means.

[0008] In the image display device as described above, in the firstsystem, a color image is formed by at least three basic color pixels ofR (red), G (green) and B (blue) as a set. Therefore, for the samedisplay area, the number of color pixels that can be displayed is ⅓ ofthat in the second system. If the number of color pixels that can bedisplayed is made equal to that in the second system, the area of thespatial light modulator becomes three times that in the second systemand the device is increased in size.

[0009] In the second system, if the response speed of the element fortime-divisionally switching three colors R (red), G (green) and B (blue)is not sufficiently high, light beams of the respective colors R, G andB appear independently and a displayed image cannot be recognized as acolor image. That is, a problem of so-called color breakup occurs.

[0010] As a switching frequency that sufficiently conceals colorbreakup, 360 Hz or higher is necessary. Therefore, the response speed ofthe switching element must be approximately 1 msec.

[0011] Also for the illuminating light illuminating the spatial lightmodulator, the respective basic colors must be switched at a high speed.This means that if an illuminating light source for emitting lightsimultaneously over all the range such as a lamp light source is used,only a part of emission spectrum of the light source can be effectivelyused at arbitrary timing and therefore the light utilization efficiencyis significantly deteriorated.

[0012] In the third system, though the problems of the above-describedfirst and second system do not occur, there are problems such asincrease in the cost of components of the spatial light modulators dueto the use of the three spatial light modulators, complexity ofadjustment for alignment of relative positions of the three spatiallight modulators, increase in the cost of components of the colorcombination system for the three colors, and increase in the size of thedevice. There is also a problem of poor reliability in positionaldeviation of the spatial light modulators with respect to each other.Moreover, in the case where the device is constructed as aprojection-type image display device, there is a problem of increase inF-number of a projection optical system due to increase of back focusingto the projection optical system. This leads to increase in the size ofthe projection optical system and increase in the manufacturing cost.

[0013] The fourth system solves the problems of the third system and hasthe following advantages, compared with the third system: a smallernumber of spatial light modulators can be used; the number of adjustmentsteps is reduced; a color combination system for two colors is enough;the device is miniaturized; and reliability in positional deviation ofthe spatial light modulator is improved.

[0014] However, it cannot solve the problems of the second system, thatis, the occurrence of color breakup in the case the response speed ofthe color switching element is not sufficiently high and lowering of thelight utilization efficiency due to the employment of the “fieldsequential system”, and the problems due to the need to switch the colorof illuminating light.

DISCLOSURE OF THE INVENTION

[0015] It is an object of this invention to provide a new image displaydevice that can solve the problems in realizing color image display bythe conventional image display device.

[0016] It is another object of this invention to provide an imagedisplay device that can be miniaturized and enables easy adjustmentduring the manufacturing process.

[0017] It is still another object of this invention to provide an imagedisplay device in which the problems of the spatial light modulator andthe problems due to color switching of illuminating light do not occur.

[0018] In order to achieve the above-described objects, an image displaydevice according to this invention includes: an illuminating lightsource for emitting illuminating light; a first spatial light modulatoron which a first wavelength range component of the illuminating lightbecomes incident and which modulates the first wavelength rangecomponent in accordance with a pixel corresponding to the firstwavelength range component; color separation and condensation meansbeing a holographic optical element for separating second and thirdwavelength range components different from the first wavelength range ofthe illuminating light and condensing the respective wavelength rangecomponents; a second spatial light modulator on which the second andthird wavelength range components are condensed and made incident atdifferent pixel positions corresponding to the second and thirdwavelength range components by the color separation and condensationmeans and which modulates these respective wavelength range componentsin accordance with pixels corresponding to the respective wavelengthrange components; and color combination means for combining modulateslight emitted from the first and second spatial light modulators.

[0019] Another image display device according to this inventionincludes: an illuminating light source for emitting illuminating light;a time division color filter on which the illuminating light becomesincident and which sequentially and alternately transmits two differentwavelength range components of the illuminating light; color separationand condensation means for condensing one wavelength range componenttransmitted through the time division color filter as a first wavelengthrange component, and for separating the other wavelength range componenttransmitted through the time division color filter into second and thirdwavelength range components and condensing the respective wavelengthrange components; and spatial light modulators for modulating the firstwavelength range component in accordance with a pixel corresponding tothe first wavelength range component when the first wavelength rangecomponent is made incident thereon by the color separation andcondensation means, and for modulating the second and third wavelengthrange components in accordance with pixels corresponding to theserespective wavelength range components when these respective wavelengthrange components are condensed and made incident at different pixelpositions corresponding to the second and third wavelength rangecomponents.

[0020] This invention provides an image display device having theadvantages of the above-described conventional first system combinedwith those of the second system, or having the advantages of the firstsystem combined with those of the fourth system.

[0021] In the image display device according to this invention, since itis not necessary to use three spatial light modulators, the problems ofthe above-described third system are solved.

[0022] According to this invention, by combining the advantages of thefirst and second systems, it is possible to display a color image withone spatial light modulator and to solve the problem of the firstsystem, that is, low definition, and the problems of the second system,that is, color breakup and low light utilization efficiency.

[0023] In the image display device according to this invention, sinceone color image is formed physically by two basic color pixels, thedefinition can be improved. As the spatial light modulator only needs toperform two-color time-division switching display, the response speedrequired of the spatial light modulator is reduced. Therefore, the colorbreakup phenomenon can be relaxed and the light utilization efficiencycan be improved.

[0024] According to this invention, by combining the advantages of thefirst and fourth system, it is possible to display a color image withtwo spatial light modulators. As the spatial light modulators, whichtime-divisionally modulates illuminating light of two colors in thefourth system, are spatially arranged on two basic color pixels as inthe first system, the problems such as color breakup and lowering oflight utilization efficiency due to employment of the “field sequentialsystem”, and the problems due to the need to switch the color of theilluminating light can be solved.

[0025] The other objects of this invention and specific advantagesprovided by this invention will be further clarified by the followingdescription of embodiments described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a plan view showing a first embodiment of an imagedisplay device according to this invention.

[0027]FIG. 2 is a longitudinal sectional view showing a lens arrayconstituting the image display device.

[0028]FIG. 3 is a plan view showing the structure of a blue/greenspatial light modulator of the image display device.

[0029]FIG. 4 is a plan view showing the structure of a red spatial lightmodulator of the image display device.

[0030]FIG. 5 is a plan view showing a second embodiment of the imagedisplay device according to this invention.

[0031]FIG. 6 is a graph showing emission spectrum of a UHP lamp used inthe image display device.

[0032]FIG. 7 is a graph showing emission spectrum of an LED lamp used inthe image display device.

[0033]FIG. 8 is a graph showing spectral diffraction efficiency of aholographic optical element used in the image display device.

[0034]FIG. 9 is a plan view showing a third embodiment of the imagedisplay device according to this invention.

[0035]FIG. 10 is a longitudinal sectional view showing the state ofmanufacturing a holographic optical element used in the image displaydevice.

[0036]FIG. 11 is a graph showing diffraction efficiency with respect towavelength and incident angle, of the holographic element used in theimage display device.

[0037]FIG. 12 is a longitudinal sectional view showing the holographicoptical element constituting the image display device.

[0038]FIG. 13 is a plan view showing the structure of a blue/greenspatial light modulator of the image display device.

[0039]FIG. 14 is a plan view showing the structure of a red spatiallight modulator of the image display device.

[0040]FIG. 15 is a plan view showing a fourth embodiment of the imagedisplay device according to this invention.

[0041]FIG. 16 is a longitudinal sectional view showing a holographicoptical element constituting the image display device.

[0042]FIG. 17 is a graph showing diffraction efficiency with respect towavelength and incident angle, of the holographic optical element usedin the image display device.

[0043]FIG. 18 is a plan view showing a fifth embodiment of the imagedisplay device according to this invention.

[0044]FIG. 19 is a longitudinal sectional view showing a holographicoptical element constituting the image display device.

[0045]FIG. 20 is a plan view showing a sixth embodiment of the imagedisplay device according to this invention.

[0046]FIG. 21 is a longitudinal sectional view showing a holographicoptical element constituting the image display device in the case of redillumination.

[0047]FIG. 22 is a longitudinal sectional view showing the holographicoptical element constituting the image display device in the case ofblue/green illumination.

[0048]FIG. 23 is a side view showing a seventh embodiment of he imagedisplay device according to this invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0049] Hereinafter, embodiments of this invention will be described indetail with reference to the drawings.

[0050] [First Embodiment]

[0051] As a first embodiment of an image display device according tothis invention, an example in which this invention is applied to atwo-plate projection-type image display device will be described.

[0052] The two-plate projection-type image display device hastransmission liquid crystal elements 50, 52 as spatial light modulators,a dichroic mirror 60 as color combination means, dichroic mirrors 40, 41as color separation means to the two transmission liquid crystalelements 50, 52, and the dichroic mirrors 40, 41 and a microlens array51 as color separation and condensation means to the one transmissionliquid crystal element, as shown in FIG. 1.

[0053] In the two-plate projection-type image display device,illuminating light emitted from a UHP lamp light source 10 as anilluminating light source becomes incident on an illuminating opticalsystem 20 having functions such as correction of the cross-sectionalshape of luminous flux, equalization of intensity, and control ofdivergence angle.

[0054] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0055] In this image display device, the illuminating light passedthrough the illuminating optical system 20 has been converted topolarized light with its electrical vector oscillating mainly in adirection perpendicular to the face of FIG. 1, that is, to S-polarizedlight to a mirror 30 on which the light becomes incident after itbecomes incident on the illuminating optical system 20.

[0056] Of the illuminating light reflected and polarized by the mirror30, only a green light component (second wavelength range component) isreflected mainly by the dichroic mirror 40 for green reflection, whichconstitutes the color separation and condensation means. Then, only ablue light component (third wavelength range component) is reflectedmainly by the dichroic mirror 41 for blue reflection, which constitutesthe arranged color separation and condensation means. These green lightcomponent and blue light component become incident on the blue/greentransmission liquid crystal element 50, which a second spatial lightmodulator having color pixels for green light modulation and colorpixels for blue light modulation. The dichroic mirror 40 for greenreflection and the dichroic mirror 41 for blue reflection are arrangedin such a manner that the incident angles on the blue/green transmissionliquid crystal element 50 of the reflected light beams of from thesedichroic mirrors are inclined by an equal angle to the verticaldirection of this element from the opposite sides.

[0057] On the incident side of the blue/green transmission liquidcrystal element 50, the microlens array 51 constituting the colorseparation and condensation means is provided. The microlens array 51 isformed on a glass board 58. By the microlens array 51, blue light B_(L)and green light G_(L) to be incident on the blue/green transmissionliquid crystal element 50 are condensed and made incident on theblue/green transmission liquid crystal element 50, corresponding to ablue color pixel 56 and a green color pixel 57, respectively, as shownin FIG. 2. The blue color pixel 56 and the green color pixel 57 areprovided corresponding to a blue color pixel electrode 53 and a greencolor pixel electrode 54 in a liquid crystal layer 55 of the blue/greentransmission liquid crystal element 50. The transmission liquid crystalelement 50 is formed by a glass board 50 a, and a common transparentelectrode 50 b is provided on the surface of each pixel.

[0058] The S-polarized light incident on the blue/green transmissionliquid crystal element 50 has its intensity modulated in accordance withthe pixels 56, 57 and is emitted as P-polarized light toward thedichroic mirror 60 as color combination means, which is a colorcombination mirror having a dielectric multilayer film, as shown in FIG.1.

[0059] On the other hand, a red light component (first wavelength rangecomponent) transmitted through the dichroic mirror 40 for greenreflection and the dichroic mirror 41 for blue reflection is reflectedby mirrors 31, 32 and then becomes incident on the red transmissionliquid crystal element (first light modulator) 52. In this redtransmission liquid crystal element 52, the red light component of theilluminating light has its intensity modulated and is emitted asS-polarized light toward the dichroic mirror 60.

[0060] The illuminating light (modulated light) modulated and emitted bythe blue/green transmission liquid crystal element 50 and theilluminating light (modulated light) modulated and emitted by the redtransmission liquid crystal element 52 are color-combined by thedichroic mirror 60 for red reflection and emitted toward a projectionoptical system 70. By the projection optical system 70, thisilluminating light is caused to form an image on a screen 80. A colorimage is displayed on this screen 80.

[0061] In this image display device, as shown in FIG. 3, the blue/greentransmission liquid crystal element 50 has a pixel structure such thatthe basic pixel pitch in the direction of arrow X is ½ of the basicpixel pitch in the pixel structure of the red transmission liquidcrystal element 52 shown in FIG. 4 and each pixel area is approximatelyhalf the pixel area in the pixel structure of the red transmissionliquid crystal element 52.

[0062] The thickness of the liquid crystal layer of the blue/greentransmission liquid crystal element 50 and the thickness of the liquidcrystal layer of the red transmission liquid crystal element 52 areoptimized in accordance with the difference of color light to bemodulated.

[0063] [Second Embodiment]

[0064] As a second embodiment of the image display device according tothis invention, an example in which this invention is applied to atwo-plate projection-type image display device will be described.

[0065] The two-plate projection-type image display device in the secondembodiment has transmission liquid crystal elements 50, 52 as spatiallight modulators, a polarized light beam splitter 61 as colorcombination means, dichroic mirrors 40, 41 as color separation means forthe two transmission liquid crystal elements 50, 52, and the dichroicmirrors 40, 41 and a microlens array 51 as color separation andcondensation means to the one transmission liquid crystal element 50, asshown in FIG. 6.

[0066] First, illuminating light emitted from a UHP lamp light source 10constituting an illuminating light source together with a red LED lightsource 11, which will be described later, becomes incident on anilluminating optical system 20 having functions such as correction ofthe cross-sectional shape of luminous flux, equalization of intensity,and control of divergence angle.

[0067] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0068] In this image display device, the illuminating light passedthrough the illuminating optical system 20 has been converted topolarized light with its electrical vector oscillating mainly in adirection perpendicular to the face of FIG. 5, that is, to S-polarizedlight to a mirror 30 on which the light becomes incident after itbecomes incident on the illuminating optical system 20.

[0069] Of the illuminating light reflected and polarized by the mirror30, only a green light component (second wavelength range component) isreflected mainly by the dichroic mirror 40 for green reflection, whichconstitutes the color separation and condensation means. Then, only ablue light component (third wavelength range component) is reflectedmainly by the dichroic mirror 41 for blue reflection, which constitutesthe arranged color separation and condensation means. These green lightcomponent and blue light component become incident on the blue/greentransmission liquid crystal element 50, which a second spatial lightmodulator having color pixels for green light modulation and colorpixels for blue light modulation. The dichroic mirror 40 for greenreflection and the dichroic mirror 41 for blue reflection are arrangedin such a manner that the incident angles on the blue/green transmissionliquid crystal element 50 of the reflected light beams of from thesedichroic mirrors are inclined by an equal angle to the verticaldirection of this element from the opposite sides.

[0070] On the incident side of the blue/green transmission liquidcrystal element 50, the microlens array 51 constituting the colorseparation and condensation means is provided. By the microlens array51, blue light and green light to be incident on the blue/greentransmission liquid crystal element 50 are condensed and made incidenton the blue/green transmission liquid crystal element 50, correspondingto a blue color pixel 56 and a green color pixel 57, respectively, asshown in FIG. 2. The blue color pixel 56 and the green color pixel 57are provided corresponding to a blue color pixel electrode 53 and agreen color pixel electrode 54 in a liquid crystal layer 55 of theblue/green transmission liquid crystal element 50.

[0071] The S-polarized light incident on the blue/green transmissionliquid crystal element 50 has its intensity modulated in accordance withthe pixels 56, 57 and is emitted as P-polarized light toward thepolarized light beam splitter 61 as color combination means, as shown inFIG. 5.

[0072] On the other hand, a red light component (first wavelength rangecomponent) transmitted through the dichroic mirror 40 for greenreflection and the dichroic mirror 41 for blue reflection is passedthrough a mirror 31, a reflection holographic optical element 42 for redlight reflection, a mirror 32 and a ½ wavelength plate 90, and becomesincident on the red transmission liquid crystal element 52. In thiscase, the red light component incident on the red transmission liquidcrystal element 52 has been converted from S-polarized light toP-polarized light by the ½ wavelength plate 90. Therefore, the lightemitted from the red transmission liquid crystal element 52 toward thepolarized light beam splitter 61 is S-polarized light.

[0073] The reflection holographic optical element 42 arranged in theoptical path between the mirror 31 and the mirror 32 has acharacteristic of mainly reflecting the spectrum of the red LED lightsource 11 constituting the illuminating light source and transmittingincident light of the other wavelength ranges. The red light emittedform the red LED light source 11 is passed through a condenser lens 22,and becomes incident on the reflection holographic optical element 42.The red light is reflected by the reflection holographic optical element42, then passed through the mirror 32 and the ½ wavelength plate 90, andbecomes incident on the red transmission liquid crystal element 52.

[0074] With respect to the emission spectrum of the UHP lamp lightsource 10, the luminance of the red wavelength range is lower than theluminance of the blue and green wavelength ranges, as shown in FIG. 6.In this image display device, light of a wavelength range of 630±10 nmis reflected by the reflection holographic optical element 42 and doesnot reach the red transmission liquid crystal element 52. In this imagedisplay device, as shown in FIG. 7, the emission spectrum of the red LEDlight source 11 corresponds to the wavelength-dependent characteristicof the reflection and diffraction efficiency of the reflectionholographic optical element 42 shown in FIG. 8. Therefore, light emittedfrom the red LED light source 11 is efficiently reflected by thereflection holographic optical element 42 for red light reflection andilluminates the red transmission liquid crystal element 52.

[0075] As shown in FIG. 5, the P-polarized light emitted from theblue/green transmission liquid crystal element 50 and the S-polarizedlight emitted from the red transmission liquid crystal element 52 arecolor-combined by the polarized light beam splitter 61 and emittedtoward a projection optical system 70. By the projection optical system70, the illuminating light incident on the projection optical system 70is caused to form an image on a screen 80. A color image is displayed onthis screen 80.

[0076] In this image display device, as shown in FIG. 3, the blue/greentransmission liquid crystal element 50 has a pixel structure such thatthe basic pixel pitch in the direction of arrow X is ½ of the basicpixel pitch in the pixel structure of the red transmission liquidcrystal element 52 shown in FIG. 4 and each pixel area is approximatelyhalf the pixel area in the pixel structure of the red transmissionliquid crystal element 52.

[0077] The thickness of the liquid crystal layer of the blue/greentransmission liquid crystal element 50 and the thickness of the liquidcrystal layer of the red transmission liquid crystal element 52 areoptimized in accordance with the difference of the color light to bemodulated.

[0078] [Third Embodiment]

[0079] As a third embodiment of the image display device according tothis invention, an example in which this invention is applied to atwo-plate projection-type image display device will be described.

[0080] The two-plate projection-type image display device in the thirdembodiment has reflection liquid crystal spatial light modulators 101,102 as spatial light modulators, a polarized light beam splitter 140 andspecific wavelength range linear polarization rotation means (multilayerphase difference filter) 120 as color combination means, dichroicmirrors 40, 41 as color separation means for the two reflection liquidcrystal spatial light modulators 101, 102, and a transmissionpolarization-selective holographic optical element 100 as colorseparation and condensation means to the one reflection liquid crystalspatial light modulator, as shown in FIG. 9.

[0081] In this two-plate projection-type image display device, first,illuminating light emitted from a UHP lamp light source 10 as anilluminating light source becomes incident on an illuminating opticalsystem 20 having functions such as correction of the cross-sectionalshape of luminous flux, equalization of intensity, and control ofdivergence angle.

[0082] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0083] In the image display device shown in FIG. 9, the illuminatinglight passed through the illuminating optical system 20 has beenconverted to polarized light with its electrical vector oscillatingmainly in a direction perpendicular to the face of FIG. 9, that is, toS-polarized light to the dichroic mirror 40 for blue reflection, thedichroic mirror 41 for green reflection and a mirror 30 on which thelight becomes incident after it becomes incident on the illuminatingoptical system 20.

[0084] The illuminating light is reflected by the dichroic mirror 40 forblue reflection and the dichroic mirror 41 for green reflection andbecomes incident on the holographic PDLC (transmissionpolarization-selective holographic optical element) 100 at differenceincident angles.

[0085] The holographic PDLC 100 used in this image display device ismanufactured by inserting PDLC, which is a mixture of polymer beforephotopolymerization (hereinafter referred to as prepolymer), nematicliquid crystal, initiator and pigment, between a pair of glass boards103, 104, as shown in FIG. 10.

[0086] In manufacturing this holographic PDLC 100, rate by weight ofnematic liquid crystal is approximately 40% of the total weight. For thethickness of this holographic PDLC 100 (hereinafter referred to as cellgap), an optimum value within a range of 3 to 15 μm is selected inaccordance with the specifications of the holographic PDLC 100.

[0087] Next, to record interference fringes on the holographic PDLC 100,object light 105 and reference light 106 are cast onto the holographicPDLC 100 from a laser light source, not shown, and variation in lightintensity (A) is generated by the interference of these lights.

[0088] In this case, at a part where the interference fringes arebright, that is, where the photon energy is large, the prepolymer in theholographic PDLC is photopolymerized into polymer by this energy. Thispolymerized part is sequentially supplied with the prepolymer from thesurrounding parts. As a result, an area where the polymerized prepolymeris dense and an area where it is sparse are formed. In the area wherethe prepolymer is dense, the concentration of nematic liquid crystal ishigh. In this manner, two areas are formed, that is, a polymerhigh-density area 107 and a liquid crystal high-density area 108.

[0089] This holographic PDLC 100 is of transmission type because it ismanufactured by casting the object light 105 and the reference light 106to the holographic PDLC 100 from the same side.

[0090] The polymer high-density area 107 in the holographic PDLC 100manufactured as described above is isotropic with respect to therefractive index. The refractive index is, for example, 1.5. On theother hand, in the liquid crystal high-density area 108 of theholographic PDCL 100, nematic liquid crystal molecules are arrayed withtheir longitudinal direction directed substantially perpendicularly tothe boundary with the polymer high-density area 107. Therefore, thisliquid crystal high-density area 108 is dependent on the direction ofincident polarized light. Of reproduced light 110 inclined with respectto a ray incident surface 109 of the holographic PDLC 100 and incidentin a direction substantially perpendicular to the direction of theboundary between the polymer high-density area 107 and the liquidcrystal high-density area 108, an S-polarized component becomes anordinary ray in the liquid crystal high-density area 108, as shown inFIG. 10.

[0091] If the refractive index nlo of the ordinary ray in the liquidcrystal high-density area 108 is set at a value substantially equal tothe refractive index np of the polymer high-density area 107, forexample, if the difference in the refractive index is less than 0.01,modulation of the incident S-polarized component based on the refractiveindex is very small and almost no diffraction occurs. Generally, thedifference Δn between the refractive index nlo of the ordinary ray ofthe nematic liquid crystal and the refractive index nle of anextraordinary ray is approximately 0.1 to 0.2. Therefore, even with thereproduced light 111 in the same incident direction, a P-polarizedcomponent, which is an extraordinary ray, is different in refractiveindex between the polymer high-density area 107 and the liquid crystalhigh-density area 108 and a diffraction effect occurs. For example, thediffraction efficiency for an extraordinary ray can be 50% or more, andthe diffraction efficiency for an ordinary ray can be 10% or less.

[0092] In this manner, the holographic PDLC 100 functions as a phasemodulation hologram with respect to the P-polarized component, which isan extraordinary ray. That is, in this holographic PDLC 100, as shown inFIG. 10, the S-polarized component, which is an ordinary ray, of thereproduced light 111, is transmitted as it is without being diffracted,whereas the P-polarized component, which an extraordinary ray, of thereproduced light 111, is diffracted and emitted substantiallyperpendicularly from the holographic PDLC 100.

[0093] The diffraction efficiency for P-polarized light of thisholographic PDLC 100 depends on the incident angle and wavelength, asshown in FIG. 11. According to this characteristic, a diffractionefficiency of 50% or higher with respect to green light having a centerwavelength of 550 nm is realized when the incident angle is 46°±8°, anda diffraction efficiency of 50% or higher with respect to blue lighthaving a center wavelength of 440 nm is realized when the incident angleis 41°±7.5°. In this manner, the incident angle on the holographic PDLC100 that realizes the optimum diffraction efficiency is differentbetween blue light and green light. Therefore, the angle of illuminatinglight incident on the holographic PDLC 100 is changed between blue lightand green light.

[0094] In the above-described holographic PDLC 100, the hologram layerhas a thickness of 4 μm, a degree of modulation of refractive index of0.06, an exposure wavelength of 532 nm, an incident angle of objectlight of 0° and an incident angle of reference light of 45°.

[0095] Actually, the holographic PDLC 100 has a single structure made upof a blue/green light hologram layer 100 a formed on a glass board 100 band is integrally constituted with the blue/green light reflectionliquid crystal spatial light modulator 101, as shown in FIG. 12. Theholographic PDLC 100 formed on a glass board 101 a has a function ofcylindrical lens having condensing capability only in one direction sothat illuminating light is condensed on a blue light pixel electrode 115and a green light pixel electrode 116 of the blue/green light reflectionliquid crystal spatial light modulator 101. A liquid crystal layer 123is formed on the blue light pixel electrode 115 and the green lightpixel electrode 116. The blue light pixel electrode 115 and the greenlight pixel electrode 116 are formed on a glass board 124.

[0096] The center of the holographic lens for each color is arranged tobe substantially coincident with the center of the corresponding colorpixel electrode. Color separation of blue light and green light of theilluminating light is realized by utilizing the difference in theincident angle between blue light (B_(L)) and green light (G_(L)) byapproximately 5° and the wavelength distribution of the holographic PDLC100.

[0097] In the case of “white” display, the illuminating light,color-separated and condensed on the respective color pixel electrodes115, 116, has its direction of incident polarization rotated 90° and isreflected as S-polarized light. Therefore, in this case, the reflectedlight is emitted substantially perpendicularly to the blue/green lightreflection liquid crystal spatial light modulator 101, without beingdiffracted by the blue light hologram layer and the green light hologramlayer.

[0098] This reflected light becomes incident on the specific wavelengthrange linear polarization rotation means (multilayer phase differencefilter) 120 such as “Color Select” manufactured by Color Link, as shownin FIG. 9. This specific wavelength range linear polarization rotationmeans 120 is an optical element formed by stacking phase differenceplates and rotates the linear polarization direction of a specificwavelength range only (in this case, blue and green light) by 90°. Thatis, this specific wavelength range linear polarization rotation means120 converts the S-polarized light modulated by the blue/green lightreflection liquid crystal spatial light modulator 101 to P-polarizedlight.

[0099] The blue and green light thus converted to P-polarized light istransmitted through the polarized light beam splitter 140, thentransmitted through red light linear polarization rotation means 121 anda polarizing plate 150 for transmitting P-polarized light, and becomesincident on the projection optical system 70. The polarized light beamsplitter 140 is constructed to transmit P-polarized light and reflectS-polarized light. The blue and green light incident on the projectionoptical system 70 forms an image on a screen, not shown.

[0100] Meanwhile, the red light transmitted through the dichroic mirror40 for blue reflection and the dichroic mirror 41 for green reflectionis reflected by the mirror 30, then detected by a polarizing plate 130for transmitting P-polarized light, and becomes incident on the specificwavelength range linear polarization rotation means 120. This specificwavelength range linear polarization rotation means 120 does not have apolarized light rotation function for red light. Therefore, the redlight is transmitted as it is through the specific wavelength rangelinear polarization rotation means 120. The red light is thentransmitted through the polarized light beam splitter 140 and becomesincident on the red light reflection liquid crystal spatial lightmodulator 102.

[0101] Of the modulated light reflected by this red light reflectionliquid crystal spatial light modulator 102, S-polarized lightcorresponding to “white” display is reflected by the polarized lightbeam splitter 140 and becomes incident on the red light linearpolarization rotation means 121. This modulated light has its directionof polarization rotated 90° by the red light linear polarizationrotation means 121 and becomes P-polarized light. This modulated lightis detected by the polarizing plate 150 and becomes incident on theprojection optical system 70. The red light incident on the projectionoptical system 70 forms an image on the screen, not shown. In thismanner, a color image is displayed on the screen.

[0102] In this image display device, as shown in FIG. 13, the pixelstructure of the blue/green reflection liquid crystal spatial lightmodulator 101 is perfectly equal to the pixel structure of the redreflection liquid crystal spatial light modulator 102 shown in FIG. 14.In the red reflection liquid crystal spatial light modulator 102, twobasic pixels as a pair corresponding to one blue light pixel 125 and onegreen light pixel 126 are equally driven as one pixel.

[0103] The thickness of the liquid crystal layer of the blue/greenreflection liquid crystal spatial light modulator 101 and the thicknessof the liquid crystal layer of the red reflection liquid crystal spatiallight modulator 102 are optimized in accordance with the difference ofthe color light to be modulated.

[0104] [Fourth Embodiment]

[0105] As a fourth embodiment of the image display device according tothis invention, an example in which this invention is applied to atwo-plate projection-type image display device will be described.

[0106] The two-plate projection-type image display device in the fourthembodiment has reflection liquid crystal spatial light modulators 101,102 as spatial light modulators, a polarized light beam splitter 140 ascolor combination means, dichroic mirrors 40, 41 as color separationmeans to the two reflection liquid crystal spatial light modulators 101,102, and a holographic PDLC (transmission polarization-selectiveholographic optical element) 111 as color separation and condensationmeans to the one reflection liquid crystal spatial light modulator, asshown in FIG. 15.

[0107] In this two-plate projection-type image display device,illuminating light emitted from a UHP lamp light source 10 as anilluminating light source becomes incident on an illuminating opticalsystem 20 having functions such as correction of the cross-sectionalshape of luminous flux, equalization of intensity, and control ofdivergence angle.

[0108] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0109] In the image display device shown in FIG. 15, the illuminatinglight passed through the illuminating optical system 20 has beenconverted to polarized light with its electrical vector oscillatingmainly in a direction parallel to the face of FIG. 15, that is, toP-polarized light to the dichroic mirror 40 for blue reflection and thedichroic mirror 41 for green reflection on which the light becomesincident after it becomes incident on the illuminating optical system20.

[0110] The illuminating light is reflected by the dichroic mirror 40 forblue reflection and the dichroic mirror 41 for green reflection andbecomes incident on the holographic PDLC 111 at difference incidentangles.

[0111] The holographic PDLC 111 used in this image display device ismanufactured by inserting PDLC, which is a mixture of polymer beforephotopolymerization, nematic liquid crystal, initiator and pigment,between a pair of glass boards. The manufacturing method for and thefunction of the holographic PDLC 111 used in this embodiment arebasically similar to those of the holographic PDLC 111 of the thirdembodiment. However, in this embodiment, the holographic PDLC 11 isconstructed to diffract S-polarized light.

[0112] Specifically, the holographic PDLC 111 functions as a phasemodulation hologram with respect to an S-polarized component, which isan extraordinary ray. That is, in this holographic PDLC 111, as shown inFIG. 16, a P-polarized component, which is an ordinary ray, ofreproduced light 110, is transmitted as it is without being diffracted,whereas an S-polarized component, which an extraordinary ray, of thereproduced light 110, is diffracted and emitted substantiallyperpendicularly from the holographic PDLC 111.

[0113] The diffraction efficiency for P-polarized light of thisholographic PDLC 111 depends on the incident angle and wavelength, asshown in FIG. 17. According to this characteristic, a diffractionefficiency of 50% or higher with respect to green light having a centerwavelength of 550 nm is realized when the incident angle is 46°±8°, anda diffraction efficiency of 50% or higher with respect to blue lighthaving a center wavelength of 440 nm is realized when the incident angleis 41°±7.5°. In this manner, the incident angle on the holographic PDLC111 that realizes the optimum diffraction efficiency is differentbetween blue light and green light. Therefore, the angle of illuminatinglight incident on the holographic PDLC 111 is changed between blue lightand green light.

[0114] In the holographic PDLC 111 used in this embodiment, the hologramlayer has a thickness of 4 μm, a degree of modulation of refractiveindex of 0.06, an exposure wavelength of 532 nm, an incident angle ofobject light of 0° and an incident angle of reference light of 45°.

[0115] Actually, the holographic PDLC 111 used here has a singlestructure made up of a blue/green light hologram layer and is integrallyconstituted with the blue/green light reflection liquid crystal spatiallight modulator 101, as shown in FIG. 12. The holographic PDLC 111 has afunction of cylindrical lens having condensing capability only in onedirection so that illuminating light is condensed on a blue light pixelelectrode 115 and a green light pixel electrode 116 of the blue/greenlight reflection liquid crystal spatial light modulator 101.

[0116] The center of the holographic lens for each color is arranged tobe substantially coincident with the center of the corresponding colorpixel electrode. Color separation of blue light and green light of theilluminating light is realized by utilizing the difference in theincident angle between blue light (B_(L)) and green light (G_(L)) byapproximately 5° and the wavelength distribution of the holographic PDLC111.

[0117] In the case of “white” display, the illuminating light,color-separated and condensed on the respective color pixel electrodes115, 116, has its direction of incident polarization rotated 90° and isreflected as S-polarized light. Therefore, in this case, the reflectedlight is emitted substantially perpendicularly to the blue/green lightreflection liquid crystal spatial light modulator 101, without beingdiffracted by the blue light hologram layer and the green light hologramlayer.

[0118] This reflected light is transmitted through the polarized lightbeam splitter 140 for transmitting P-polarized light and reflectingS-polarized light, then transmitted through red light linearpolarization rotation means 121 and a polarizing plate 150 fortransmitting P-polarized light, and becomes incident on a projectionoptical system 70. The polarized light beam splitter 140 is constructedto transmit P-polarized light and reflect S-polarized light. The blueand green light incident on the projection optical system 70 forms animage on a screen, not shown.

[0119] Meanwhile, red light emitted from a red LED light source 11provided separately from the UHP lamp light source 10 is passed througha condenser lens 22, the transmitted through the polarized light beamsplitter 140, and becomes incident on the red light reflection liquidcrystal spatial light modulator 102. Of the modulated light reflected bythis red light reflection liquid crystal spatial light modulator 102,S-polarized light corresponding to “white” display is reflected by thepolarized light beam splitter 140, then has its direction ofpolarization rotated 90° by the red light linear polarization rotationmeans 121, and becomes P-polarized light. This modulated light isdetected by the polarizing plate 150 and becomes incident on theprojection optical system 70. The red light incident on the projectionoptical system 70 forms an image on the screen, not shown. In thismanner, a color image is displayed on the screen.

[0120] In this image display device, as shown in FIG. 13, the pixelstructure of the blue/green reflection liquid crystal spatial lightmodulator 101 is perfectly equal to the pixel structure of the redreflection liquid crystal spatial light modulator 102 shown in FIG. 14.In the red reflection liquid crystal spatial light modulator 102, twobasic pixels as a pair corresponding to one blue light pixel 125 and onegreen light pixel 126 are equally driven as one pixel.

[0121] The thickness of the liquid crystal layer of the blue/greenreflection liquid crystal spatial light modulator 101 and the thicknessof the liquid crystal layer of the red reflection liquid crystal spatiallight modulator 102 are optimized in accordance with the difference ofthe color light to be modulated.

[0122] [Fifth Embodiment]

[0123] As a fifth embodiment of the image display device according tothis invention, an example in which this invention is applied to atwo-plate projection-type image display device will be described.

[0124] The two-plate projection-type image display device in the fifthembodiment has reflection liquid crystal spatial light modulators 101,102 as spatial light modulators, a polarized light beam splitter 141 ascolor combination means, a holographic PDLC 122 as color separationmeans to the two reflection liquid crystal spatial light modulators 101,102, and a holographic PDLC 112 as color separation and condensationmeans to the one reflection liquid crystal spatial light modulator 101,as shown in FIG. 18.

[0125] First, illuminating light emitted from a UHP lamp light source 10as an illuminating light source becomes incident on an illuminatingoptical system 20 having functions such as correction of thecross-sectional shape of luminous flux, equalization of intensity, andcontrol of divergence angle.

[0126] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0127] In this embodiment, the illuminating light passed through theilluminating optical system 20 has been converted to polarized lightwith its electrical vector oscillating mainly in a direction parallel tothe face of FIG. 18, that is, to P-polarized light to a mirror 30 onwhich the light becomes incident after it becomes incident on theilluminating optical system 20.

[0128] The illuminating light is detected by a polarizing plate 151 fortransmitting P-polarized light, then only has its red light componentconverted to S-polarized light by red light linear polarization rotationmeans (multilayer phase difference filter) 121, and becomes incident onthe holographic PDLC (transmission polarization-selective holographicoptical element) 122. This holographic PDLC 122 diffracts onlyP-polarized light and transmits S-polarized light, like the holographicPDLC 100 of the above-described third embodiment. Therefore, blue andgreen light is diffracted by this holographic PDLC 122 and red light istransmitted through the holographic PDLC 122 as it is.

[0129] The blue and green light diffracted by the holographic PDLC 122passes through a place of incidence of a coupling prism 160 and becomesincident on the holographic PDLC 112 optically joined with the couplingprism 160. Also this holographic PDCL 112 has a function of diffractingonly P-polarized light and transmitting S-polarized light, like theholographic PDCL 100 of the above-described third embodiment.

[0130] The holographic PDLC 112 of this embodiment has a stackedtwo-layer structure in which a blue light hologram layer 113 and a greenlight hologram layer 114 are provided as two layers with glass boards100 c, 100 d, and the holographic PDLC 112 is integrally constructedwith the blue/green light reflection liquid crystal spatial lightmodulator 101, as shown in FIG. 19. The holographic PDLC 112 has afunction of cylindrical lens having condensing capability only in onedirection so that illuminating light is condensed on a blue light pixelelectrode 115 and a green light pixel electrode 116 of the blue/greenlight reflection liquid crystal spatial light modulator 101. The centerof the holographic lens for each color is arranged to be substantiallycoincident with the center of the corresponding color pixel electrode.

[0131] The blue light pixel electrode 115 and the green light pixelelectrode 116 are formed on a glass board 127. A liquid crystal layer128 is formed on the electrodes 115, 116. Moreover, a glass board 129 isprovided thereon.

[0132] In the case of “white” display, the illuminating light,color-separated and condensed on the respective color pixel electrodes115, 116, has its direction of incident polarization rotated 90° and isreflected as S-polarized light. Therefore, in this case, the reflectedlight is emitted substantially perpendicularly to the blue/green lightreflection liquid crystal spatial light modulator 101, without beingdiffracted by the blue light hologram layer 113 and the green lighthologram layer 114.

[0133] The modulated light, which is S-polarized light reflected by theblue/green light reflection liquid crystal spatial light modulator 101,passes through the coupling prism 160 again and has its direction ofpolarization rotated by 90° by a ½ wavelength plate 170 to becomeP-polarized light, as shown in FIG. 18. Then, this modulated light istransmitted through the polarized light beam splitter 141 fortransmitting P-polarized light and reflecting S-polarized light andbecomes incident on a projection optical system 70. The blue and greenlight incident on the projection optical system 70 forms an image on ascreen, not shown.

[0134] Meanwhile, the red light, which is S-polarized light transmittedthrough the holographic PDLC 122, is reflected by the mirror 30, thenconverted to P-polarized light by the ½ wavelength plate 170, andbecomes incident on the polarized light beam splitter 141. Then, the redlight is transmitted through a polarized light separation film of thispolarized light beam splitter 141 and becomes incident on the red lightreflection liquid crystal spatial light modulator 102. Of the modulatedlight reflected by the red light reflection liquid crystal spatial lightmodulator 102, S-polarized light corresponding to “white” display isreflected by the polarized light separation film of the polarized lightbeam splitter 141 and combined with the blue and green light. Thismodulated light becomes incident on the projection optical system 70.The red light incident on the projection optical system 70 forms animage on the screen, not shown. In this manner, a color image isdisplayed on the screen.

[0135] In this image display device, as shown in FIG. 13, the pixelstructure of the blue/green reflection liquid crystal spatial lightmodulator 101 is perfectly equal to the pixel structure of the redreflection liquid crystal spatial light modulator 102 shown in FIG. 14.In the red reflection liquid crystal spatial light modulator 102, twobasic pixels as a pair corresponding to one blue light pixel 125 and onegreen light pixel 126 are equally driven as one pixel.

[0136] The thickness of the liquid crystal layer of the blue/greenreflection liquid crystal spatial light modulator 101 and the thicknessof the liquid crystal layer of the red reflection liquid crystal spatiallight modulator 102 are optimized in accordance with the difference ofthe color light to be modulated.

[0137] [Sixth Embodiment]

[0138] As a sixth embodiment of the image display device according tothis invention, an example in which this invention is applied to asingle-plate projection-type image display device will be described.

[0139] The single-plate projection-type image display device in thesixth embodiment has a holographic PDLC (transmissionpolarization-selective holographic optical element) 117 as colorseparation and condensation means to a reflection liquid crystal spatiallight modulator 118, as shown in FIG. 20.

[0140] In this image display device, illuminating light emitted from aUHP lamp light source 10 as an illuminating light source becomesincident on an illuminating optical system 20 having functions such ascorrection of the cross-sectional shape of luminous flux, equalizationof intensity, and control of divergence angle.

[0141] The illuminating optical system 20 has polarization conversionmeans 21 called P-S polarization converter having a function ofuniformly converting unpolarized luminous fluxes to either P-polarizedlight or S-polarized light at an efficiency of 50% or higher. Thisilluminating optical system 20 includes plural condenser lenses and thepolarization conversion means 21.

[0142] In this image display device, the illuminating light passedthrough the illuminating optical system 20 has been converted topolarized light with its electrical vector oscillating mainly in adirection parallel to the face of FIG. 20, that is, to P-polarized lightto dichroic mirrors 43, 41 and 40 on which the light becomes incidentafter it becomes incident on the illuminating optical system 20.

[0143] As this illuminating light sequentially passes through thedichroic mirror 43 for red reflection, the dichroic mirror 41 for greenreflection and the dichroic mirror 40 for blue reflection, its redcomponent, green component and blue component are reflected. These redcomponent, green component and blue component of the illuminating lightbecome incident on a color wheel 180. This color wheel 180time-divisionally switches red light and cyan (blue+green) light. Thecolor light components passed through the color wheel 180 becomeincident on the holographic PDLC 117 at different incident angles,respectively.

[0144] The structure of the holographic PDLC 117 used in this embodimentis adapted for diffracting P-polarized light and not diffractingS-polarized light, like the holographic PDLC 100 used in theabove-described third embodiment. This holographic PDLC 117 has astructure in which hologram layers for R, G, B light 131, 132, 133 arestacked as three layers with glass board 134, 135, 136, and theholographic PDLC 117 is integrally constructed with the reflectionliquid crystal spatial light modulator 118, as shown in FIGS. 21 and 22.

[0145] The holographic PDLC 117 has a function of cylindrical lenshaving condensing capability only in one direction so that illuminatinglight is condensed on a corresponding basic pixel of each color of thereflection liquid crystal spatial light modulator 118.

[0146] In the case where the red light component of the illuminatinglight is selected by the color wheel 180 and made incident on theholographic PDLC 117, the illuminating light is diffracted only by thered light hologram layer 131 of the holographic PDCL 117 and condensedon all basic pixel electrodes 119 a, 119 b of the reflection liquidcrystal spatial light modulator 118, as shown in FIG. 21. In imagedisplay, since two adjacent basic pixel electrodes 119 a, 119 b are usedas one pixel electrode 119, these adjacent two pixel electrodes 119 a,119 b are equally driven as one pixel electrode 119.

[0147] Also in the reflection liquid crystal spatial light modulator118, the pixel electrodes 119 are formed on a glass board 137. A liquidcrystal layer 138 is provided on the pixel electrodes 119. Theholographic PDLC 117 is provided over this with a glass board 139provided between the holographic PDLC 117 and the liquid crystal layer138.

[0148] Next, in the case where the blue light component and the greenlight component of the illuminating light are selected by the colorwheel 180 and made incident on the holographic PDLC 117, these colorcomponents of the illuminating light are diffracted by the blue lighthologram layer 133 and the green light hologram layer 132, respectively,and condensed on the corresponding basic pixel electrodes 119 a, 119 bof the holographic PDLC 117, as shown in FIG. 22.

[0149] In this reflection liquid crystal spatial light modulator 118,the two basic pixel electrodes for red light modulation as a pair in redlight modulation, and the basic pixel electrode for blue lightmodulation and the basic pixel electrode for green light modulation inblue and green light modulation, that is, four pixel electrodes intotal, are driven as one pixel to realize color image display. Of thesefour pixel electrodes in total, the two basic pixel electrodes for redlight modulation will be later used as the basic pixel electrode forblue light modulation and the basic pixel electrode for green lightmodulation. Therefore, it can be considered that there are physicallytwo pixel electrodes.

[0150] In the holographic PDLC 117, since the hologram layers 131 to 133are stacked, the diffracted light diffracted by the red hologram layer131 and the green hologram layer 132, which are upper layers, isdiffracted again by the blue hologram layer 133, which is a lower layer.Therefore, a part of the illuminating light does not illuminate thereflection liquid crystal spatial light modulator 118.

[0151] To prevent this, it is necessary to sufficiently narrow thespreading angle of the illuminating light to be cast, for example, toapproximately ±3°, and narrow the wavelength range of each color light,for example, to approximately ±20 nm. Moreover, it is necessary toreduce the allowable diffraction angle of each hologram layer.Therefore, in this embodiment, the illuminating light is set to beincident on the hologram layers at a sufficiently large angle, forexample, 65°, using a coupling prism 160.

[0152] In the case of “white” display, the illuminating light,color-separated and condensed on the respective color pixel electrodes119 a, 119 b of the reflection liquid crystal spatial light modulator118, has its direction of incident polarization rotated 90° and isreflected as S-polarized light. Therefore, in this case, the reflectedlight is emitted substantially perpendicularly to the reflection liquidcrystal spatial light modulator 118, without being diffracted by therespective color light hologram layers (R, G, B).

[0153] This reflected light passes through the coupling prism 160 again,then detected by a polarizing plate 150 for transmitting S-polarizedlight, and becomes incident on a projection optical system 70, as shownin FIG. 20. The reflected light incident on the projection opticalsystem 70 forms an image on a screen, not shown. In this manner, a colorimage is displayed on the screen.

[0154] [Seventh Embodiment]

[0155] As a seventh embodiment of the image display device according tothis invention, an example in which this invention is applied to avirtual image display device will be described.

[0156] The virtual image display device has EL image display elements101, 102 as two spatial light modulators, a dichroic mirror 60, and aneyepiece lens 190, as shown in FIG. 23.

[0157] In this image display device, display light from the EL imagedisplay element 101 for red light emission and display light from the ELimage display element 102 for green/blue light emission are combined bythe dichroic mirror 60 for red reflection, then passes through theeyepiece lens 190, and makes virtual image display to an eye 191.

[0158] In this image display device, as shown in FIG. 3, the EL displayelement 102 for blue/green light emission has a pixel structure suchthat the basic pixel pitch in the direction of arrow X is ½ of the basicpixel pitch in the pixel structure of the EL display element 101 for redlight emission shown in FIG. 4 and each pixel area is approximately halfthe pixel area in the pixel structure of the EL display element 101 forred light emission.

[0159] Industrial Applicability

[0160] As described above, the image display device according to thisinvention realizes color image display by using one or two spatial lightmodulators. Therefore, the number of spatial light modulators to be usedcan be reduced and the device itself can be miniaturized. Moreover, thepositions of the spatial light modulators can be easily adjusted andaccurate positional alignment of the spatial light modulators can beeasily realized.

[0161] Moreover, the image display device according to this inventioncan avoid increase in F-number of a projection optical system due toincrease of back focusing to the projection optical system required inthe case of a projection-type image display device, and thereforeenables reduction in the manufacturing cost.

[0162] In the image display device according to this invention, evenwhen a spatial light modulator with a relatively low response speed isused, since the spatial light modulator has a two-plate structure, thedefinition of a displayed image is not significantly lowered and colorimage display having no color breakup with high light utilizationefficiency can be realized.

[0163] In the image display device according to this invention, if aspatial light modulator that has a relatively high response speed andcan realize two-color switching display at a level where color breakupdoes not occur is used, color image display with high light utilizationefficiency can be realized by a single-plate structure.

[0164] In the image display device according to this invention, byseparating and condensing color light corresponding to two basic colorpixels physically formed in one spatial light modulator onto the twobasic color pixels, it is possible to realize a highly efficient imagedisplay element.

[0165] Moreover, by using a polarization-selective holographic opticalelement using an anisotropic material such as a liquid crystal materialas a holographic optical element, it is possible to realize moreefficient color image display.

[0166] In the image display device according to this invention, when twospatial light modulators are used, by using the spatial light modulatorhaving a color pixel for modulating one wavelength range as a spatiallight modulator for red light modulation and using the spatial lightmodulator having a color pixel for modulating two different wavelengthranges as a spatial light modulator for blue and green light modulation,it is possible to realize highly efficient color image display with goodcolor balance.

[0167] When one spatial light modulator is used, by using light beams oftwo colors emitted from a time division color filter as red light andcyan light and illuminating the spatial light modulator with theselights, it is possible to realize highly efficient color image displaywith good color balance.

[0168] In the image display device according to this invention, when twospatial light modulators are used, by using a second light source thatmainly emits red light and illuminating the spatial light modulatorhaving a color pixel for modulating one wavelength range with the secondlight source, it is possible to realize highly efficient color imagedisplay with good color balance.

1. An image display device comprising: an illuminating light source foremitting illuminating light; a first spatial light modulator on which afirst wavelength range component of the illuminating light becomesincident and which modulates the first wavelength range component inaccordance with a pixel corresponding to the first wavelength rangecomponent; color separation and condensation means being a holographicoptical element for separating second and third wavelength rangecomponents different from the first wavelength range of the illuminatinglight and condensing the respective wavelength range components; asecond spatial light modulator on which the second and third wavelengthrange components are condensed and made incident at different pixelpositions corresponding to the second and third wavelength rangecomponents by the color separation and condensation means and whichmodulates these respective wavelength range components in accordancewith pixels corresponding to the respective wavelength range components;and color combination means for combining modulates light emitted fromthe first and second spatial light modulators.
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 13. The imagedisplay device as claimed in claim 1, wherein the holographic opticalelement is a polarization-selective holographic optical elementcontaining a liquid crystal material.
 14. The image display device asclaimed in claim 1, wherein illuminating light incident on theholographic optical element is P-polarized light.
 15. The image displaydevice as claimed in claim 1, wherein the holographic optical elementhas a diffraction efficiency of 50% or more for P-polarized light and adiffraction efficiency of 10% or less for S-polarized light.
 16. Theimage display device as claimed in claim 1, wherein in the holographicoptical element, two types of holographic lenses, that is, a holographiclens for green diffraction and a holographic lens for blue diffraction,are formed by stacking plural hologram layers or by multiple exposure ofone hologram layer.
 17. The image display device as claimed in claim 1,further comprising color separation means made up of a holographicoptical element on which the illuminating light from the illuminatinglight source becomes incident, wherein the color separation meansdiffracts one of blue and green light, which is the second and thirdwavelength range components of the illuminating light, and red light,which is the first wavelength range component of the illuminating light,and does not diffract the other, thereby separating the blue and greenlight from the red light, and the color separation means causes the redlight to be incident on the first spatial light modulator and causes theblue and green light to be incident on the holographic optical elementwhich is the color separation and condensation means.
 18. The imagedisplay device as claimed in claim 1, wherein the second spatial lightmodulator has, in different pixels corresponding to the second and thirdwavelength range components, a color filter corresponding to eachwavelength range.
 19. The image display device as claimed in claim 18,wherein the first and second spatial light modulators are reflectionspatial light modulators.
 20. The image display device as claimed inclaim 18, wherein the color combination means is a color combinationmirror having a dielectric multilayer film.
 21. The image display deviceas claimed in claim 18, wherein the color combination means is apolarized light beam splitter.
 22. The image display device as claimedin claim 18, wherein the color combination means is a holographicoptical element.
 23. The image display device as claimed in claim 18,wherein the pixel in the first spatial light modulator is a pixel for ared light modulation, and the pixels of the second spatial lightmodulator are a pixel for blue light modulation and a pixel for greenlight modulation.
 24. The image display device as claimed in claim 18,wherein the illuminating light source includes plural light sourceshaving difference emission wavelength ranges and illuminating lightemitted from at least one light source illuminates only one of the firstand second spatial light modulators.
 25. The image display device asclaimed in claim 18, further comprising color separation means forseparating the illuminating light into the first wavelength rangecomponent and a range component including the second and thirdwavelength range components, causing the first wavelength rangecomponent to be incident on the first spatial light modulator, andcausing the range component including the second and third wavelengthrange components to be incident on the color separation and condensationmeans.
 26. The image display device as claimed in claim 18, wherein thefirst and second spatial light modulators have equal pixel structuresand display areas.
 27. The image display device as claimed in claim 18,wherein the number of pixels in the first spatial light modulator is ½of the number of pixels in the second spatial light modulator and itsdisplay area is equal to that of the second spatial light modulator. 28.An image display device comprising: an illuminating light source foremitting illuminating light; a time division color filter on which theilluminating light becomes incident and which sequentially andalternately transmits two different wavelength range components of theilluminating light; color separation and condensation means forcondensing one wavelength range component transmitted through the timedivision color filter as a first wavelength range component, and forseparating the other wavelength range component transmitted through thetime division color filter into second and third wavelength rangecomponents and condensing the respective wavelength range components;and spatial light modulators for modulating the first wavelength rangecomponent in accordance with a pixel corresponding to the firstwavelength range component when the first wavelength range component ismade incident thereon by the color separation and condensation means,and for modulating the second and third wavelength range components inaccordance with pixels corresponding to these respective wavelengthrange components when these respective wavelength range components arecondensed and made incident at different pixel positions correspondingto the second and third wavelength range components.
 29. The imagedisplay device as claimed in claim 28, wherein two wavelength rangecomponents transmitted by the time division color filter are red lightand cyan light.
 30. The image display device as claimed in claim 28,wherein the spatial light modulator is a reflection spatial lightmodulator.
 31. The image display device as claimed in claim 28, whereinthe illuminating light source includes plural illuminating light sourceshaving difference emission wavelength ranges and illuminating lightemitted from at least one illuminating light source illuminates only oneof the spatial light modulators.
 32. The image display device as claimedin claim 28, further comprising color separation means for separatingthe different wavelength range components of the illuminating light tothe first spatial light modulator and the second spatial lightmodulator.
 33. The image display device as claimed in claim 28, whereinthe color separation and condensation means is a holographic opticalelement.
 34. The image display device as claimed in claim 33, whereinthe holographic optical element is a polarization-selective holographicoptical element containing a liquid crystal material.
 35. The imagedisplay device as claimed in claim 33, wherein illuminating lightincident on the holographic optical element is P-polarized light. 36.The image display device as claimed in claim 33, wherein the holographicoptical element has a diffraction efficiency of 50% or more forP-polarized light and a diffraction efficiency of 10% or less forS-polarized light.
 37. The image display device as claimed in claim 33,wherein in the holographic optical element, three types of holographiclenses, that is, a holographic lens for red diffraction, a holographiclens for green diffraction and a holographic lens for blue diffraction,are formed by stacking plural hologram layers or by multiple exposure ofone hologram layer.
 38. The image display device as claimed in claim 37,wherein the area of one said holographic lens for red diffraction is ½of the area of one said holographic lens for green diffraction and saidholographic lens for blue diffraction.
 39. (Deleted)
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